Lysates were clarified from sonicated nuclei using a Diagenode Bioruptor (3 rounds of 12 cycles) and histone-DNA complexes were isolated with antibody. Libraries were prepared according to NEB instructions accompanying the NEBNext® DNA Library Prep Kit for Illumina. Briefly, DNA was end-repaired using a combination of T4 DNA polymerase, E. coli DNA Pol I large fragment (Klenow polymerase) and T4 polynucleotide kinase. The blunt, phosphorylated ends were treated with Klenow fragment (32 to 52 exo minus) and dATP to yield a protruding 3- 'A' base for ligation of Illumina's adapters which have a single 'T' base overhang at the 3’ end. After adapter ligation DNA was PCR amplified with Illumina primers for 10-15 cycles and library fragments of ~250 bp (insert plus adaptor and PCR primer sequences) were band isolated from an agarose gel.